1. Field of the Invention
The invention relates in general to a semiconductor device and a method of fabricating the same, and more particularly to a semiconductor device with two doped regions adjacent to the channel region and a method of fabricating the same.
2. Description of the Related Art
Recently, a part of the semiconductive circuits, such as the pixel circuit and the driving circuit, applied to the active-matrix display, have been directly formed on the glass substrate. More semiconductive circuits, such as memory circuits and logic circuits, are also disposed on the glass substrate for to reduce cost. Polysilicon transistor technology, which is characterized by high carrier mobility, is preferably applied to memory circuits or logic circuits that ought to be operated in high velocity. In general, low temperature polysilicon (LTPS) technology is in the mainstream of methods for fabricating polysilicon transistors, as the glass and the circuits formed on it undergo lower temperature and less damage during the fabricating process. Among LTPS technology, attention is focused upon the metal induced crystallization (MIC) process because it is characterized by high displaying uniformity, reduced number of compensating circuits used in pixel circuits, high yield, and high opening ratio. During the MIC process, the metal, so-called catalyst, is doped into the amorphous silicon to decrease the required temperature at which amorphous silicon is able to be transformed to polysilicon.
However, if the catalyst were left in the polysilicon layer, the channel region composed of polysilicon and catalyst would become defective, so as to cause leakage of current. Even if the XV group elements or halogen were added to the polysilicon layer other than in the channel region to attract the catalyst from the channel region, the catalyst which remains in the channel region after this treatment, still results in a deep level defect and leakage of current so as to make the character of the transistor deteriorate.